1. Field of the Invention
The present invention relates to cationic microgels and to their use in cationic electrodeposition.
2. Brief Description of the Prior Art
Electrodeposition as a coating application method involves the deposition of a film-forming composition under the influence of an applied electrical potential. Electrodeposition has become increasingly important in the coatings industry because by comparison with non-electrophoretic coating means, electrodeposition offers higher paint utilization, outstanding corrosion protection and low environmental contamination. Initially, electrodeposition was conducted with the workpiece being coated serving as the anode. This was familiary referred to as anionic electrodeposition. However, cationic electrodeposition has mainly replaced the older anionic electrodeposition and by today is the far most prevalent method of electrodeposition. Throughout the world, more than 80 percent of all motor vehicles produced are given a primer coating by cationic electrodeposition. Other areas of application are primer coatings or one-coat topcoatings of automobile accessories, farm machinery, house and electrical appliances, steel furniture and structural components.
A serious problem associated with electrodeposition as practiced industrially is in coverage over edges of the substrate being coated. The coating is relatively thin in these edge areas which results in the tendency for early and severe corrosion at the edge. The edge coverage can be improved if the inorganic pigment level of the bath is increased but this results in unacceptable roughness of the resultant coating.